The series stars Georgina Sherrington and Felicity Jones, and is based on The Worst Witch books by Jill Murphy.
The girls have the idea that if Mildred had the opportunity to save the school from destruction, as she had done before, then it would count in her favour and Miss Cackle would reinstate them.
They then decide to summon a mythical monster from a dangerous book called the 'Mytheocopia' with the intention that Mildred and Jadu would save the day, but the plan goes horribly wrong when they accidentally summon 'The Uninvited' - an evil witch who sets about putting everyone in the castle into a deep sleep.
Mildred, Jadu and Drusilla then use Prince Percy to wake everyone who has been put to sleep with a single kiss to the lips.
Miss Hardbroom battles the evil witch but is overpowered, and it is left to Mildred to save the day by returning The Uninvited to the Mytheocopia using her special ability.